There are cases where characters should be input to a portable apparatus such as a cellular phone, a terminal device with a display disposed at a bank or a round-the-clock store (e.g. ATM (Automatic Teller's Machine) and a terminal at a kiosk), a television receiver (hereinafter referred to as a Web television receiver) connectable to the Internet to display a Web page and the like. In this case, a person who executes character input operation (hereinafter referred to as a user) is in some cases demanded to input characters without the others' knowing the input characters. Relevant case is, for example, a case where secret information such as a password is input.
In general, for preventing others than a user from knowing an input character, the input character is replaced by a blank (e.g. “*”) and displayed. Such a character input system is, however, premised on that a key for use in character input and a character correspond one-for-one to each other. In a case of a remote controller of a Web television receiver or a cellular phone having a small number of keys, accordingly, kinds of characters which can be input are limited. Characters which can be input are limited to numerals, for example. With an input device having none of number keys (e.g. an input device having a direction indicator key such as up, down, right and left but not a number key), for example, characters such as password themselves can not be input.
Known as a character input method is a method using a soft keyboard by which with a virtual keyboard displayed on a screen, keys are clicked by a mouse. Also known is a method of switching a character on a cellular phone every time a number key is pressed and determining a character according to the number of presses of the number key.
Among systems proposed is a character input system for inputting a character without having a third person know a character to be input (e.g. see Literature 1 and Literature 2). Recited in Literature 1 is the character input system in which with two-dimensionally aligned character strings displayed, a user operates a button for selecting a column and a button for selecting a row to determine one character as an input character. Recited in Literature 2 is the character input device in which with a focus successively moved in a predetermined cycle along an input candidate character string displayed on a display screen, a user operates a button or the like when the focus moves to a character that the user wants to input to select the input character. In the character input device recited in Literature 2, when inputting one character, the focus is moved at least once on an individual character of the input candidate character string.    Literature 1: Japanese Patent Laying Open No. 2005-316961 (paragraphs 0030-0035, FIG. 2, FIG. 4).    Literature 2: Japanese Patent Laying Open No. 2005-78251 (paragraphs 0016-0029).
With the character input system recited in Literature 1, one character is determined by operating a button for selecting a column and a button for selecting a row. When increasing the number of characters as input candidates, however, the number of columns and rows of two-dimensionally aligned character strings is increased. Although in the character input system illustrated in Literature 1, for example, upper-case letters are excluded from input candidates (see FIG. 4 in Literature 1), the number of the columns and the rows of the character strings will be large when upper-case letters are included in input candidates. Then, the number of buttons for selecting the columns and buttons for selecting the rows will be accordingly increased. As a result, the system has a difficulty in application to a case where the number of keys is small.
In the character input device recited in Literature 2, when inputting one character, the focus is moved onto an individual character of an input candidate character string at least once. Therefore, the larger the number of kinds of characters as input candidates is, the more time is required for inputting one character, thereby making efficient (in other words, quick) character input difficult. When a focus moving speed is increased for speeding up character input, because time when the focus remains at one input candidate character will be shortened, erroneous input is more likely to occur. In addition, because for enhancing secrecy, it is not displayed such as at which selection candidate character the focus remains when the button is pressed, a user is not allowed to notice erroneous input even he/she makes it.
On the other hand, with character input by a soft keyboard and a character input method in which a character is determined according to the number of times of pressing of a number key, when a third person sees a display screen, input characters will be known to the third person.
An exemplary object of the present invention is to provide a character input system, a character input method and a character input program which enable various kinds of characters and symbols to be efficiently input without having others know them even when the number of keys is small.